Rolling mill including means for compensating for roll bending

ABSTRACT

The disclosure of this invention pertains to a rolling mill having an hydraulic piston cylinder assembly for bending the rolls to compensate for roll deflection caused by the separating force. One of the rolls is adjusted by other hydraulic piston cylinder assemblies and the separating force is measured by load cells. A control device is provided for receiving a separating force signal from the cells and for controlling the operation of the roll bending and roll adjusting piston cylinder assemblies to maintain the forces thereof at a desired relationship relative to a variation of the separating force.

United States Patent [191 Marten [451 Apr. 15, 1975 [75] Inventor:Hans-Friedrich Marten, Kreuztal,

Germany [73] Assignee: Schloemann-Siemag Aktiengesellschaft [22] Filed:Dec. 28, I973 [21] Appl. No.: 429,424

[30] Foreign Application Priority Data Dec. 30, 1972 Germany 2264333[52] US. Cl. 72/8; 72/21; 72/245 [51] Int. Cl B2lb 37/00 [58] Field ofSearch 72/8, 20, 19, 237, 241, 72/245, 21

[56] References Cited UNITED STATES PATENTS 2,903,926 9/1959 Reichl 72/83,416,341 12/1968 Dey et al. 72/21 X 3,518,858 7/1970 Kamata 72/193,620,058 11/1971 Sabatini et a1. 72/8 3,793,859 2/1974 Sterrett et al.72/20 X Primary Exdm'inerMilton S. Mehr Attorney, Agent, or Firm-DanielPatch; Henry C. Westin [57] ABSTRACT The disclosure of this inventionpertains to a rolling mill having an hydraulic piston cylinder assemblyfor bending the rolls to compensate for roll deflection caused by theseparating force. One of the rolls is adjusted by other hydraulic pistoncylinder assemblies and the separating force is measured by load cells.A control device is provided for receiving a separating force signalfrom the cells and for controlling the operation of the roll bending androll adjusting piston cylinder assemblies to maintain the forces thereofat a desired relationship relative to a variation of the separatingforce.

9 Claims, 4 Drawing Figures PATENTEDAPRI 5:915 3, 877, 270

sum 2 9f '3 ROLLING MILL INCLUDING MEANS FOR COMPENSATING FOR ROLLBENDING It is known to reduce the bending of rolls of a rolling millstand caused by the roll separating forces by inducing counteractingbending forces with the aid of bending bearings installed on theextended necks of rolls. The systems known and applied and manufactureddevices have the disadvantage that the range of control and adjustmentis very limited due to the fact that the roll bending causes mainly abending of the extended necks of rolls, and the actual roll bodies whichare constructed with a large diameter and a high moment of inertia areonly slightly elastically deformed by the moments transferred to them.

The high bending forces that must be produced to bend the rolls resultin an additional load of the stand, causing an increased swelling of thestand, and are the cause for unwanted changes to the roll gap and, withthis, of the thickness of the rolled stock. For the reason, the screwingdown of rolls must be changed with each adjustment of the roll bending,if the thickness of the rolled stock is to be brought back to thedesired thickness. Therefore, the known systems and devices for theadjustment or the control of the bending of rolls have not only theabove-mentioned disadvantage of the limited range of control, but alsoan unwanted influence on the thickness of the rolled stock and adetrimental effect as far as the tolerance of the finished rolled stockis concerned.

It has been suggested not to use the spindle screwdown mechanism of aroll stand for the automatic control of the thickness of rolled strips,but instead to additionally change the roll bending force in proportionto the changes of the roll separating forces caused by the variousthicknesses of rolled strips. This eliminates an increased bending ofthe rolls when harder or thicker lengths of rolled strips pass the standso that the thickness measured in the center of the rolled strip showsless tolerances as would be the case without the application of such acontrol. The increased load of the stand causes an increased swelling ofit which enlarges the roll gap itself. On principle, variations in thelengths cannot be compensated in this manner, and the application ofstrip tensions, differing over the width of the strip is favored.

The present invention has for one of its objects the consturcting of aroll stand in which the counteracting roll bending forces fro the rollor rolls can be derived from the changes of the roll separating forces,without the need of employing a control device.

With the application of such an arrangement these forces allow for aquick acting adjustment of the roll bending with only unimportanteffects on the roll gap, and a roll gap which is largely constant overits entire length will be attained,and consequently, a uniform shape ofthe rolled stock as well as a uniform thickness of the rolled stock.

The invention has the further object of designing a simple control in amanner that an adjustment of the cross section of the roll gap accordingto specified cross sections of the entering strip is possible, in orderto guarantee that the strip can be rolled free of tension.

Another purpose of the invention is to design a roll stand in such amanner that the desired roll bending can be attained with relatively lowroll bending forces which load the stand only to an unimportant extent.

Another aim of the invention is to design a skin-pass stand whichdischarges a product which is free of tension when a skin-pass rate ofelongation has been specified. This can be attained by providing anadjusting device which will keep the screwdown forces (P and the rollbending cylinder force (P always in proportion to each other, in whichthe proportional factor results from a distance a of a line whichdivides the first from the second adjacent quarters of the effectivewidth of the rolled stock, from the center of the adjacent main bearing,and a distance b of the line of application of the restoring force, fromthe center of said adjacent main bearing according to the followingequation:

m PA1 1/(b/a+ 1 The roll bending forces which are necessary for thebending of the back-up rolls are considerably reduced when the diametersof the necks of the back-up rolls for four-high roll stands are 0.8 ofthe diameters of the roll bodies. A control of the thickness of stripscan be obtained when the parts of the opposed main bearings are equippedwith motion or position pickups which measure their distance, and when acontrol device is provided for maintaining a specified distance of theseparts. The motion or position pickups can be arranged ahead of thecontrol device.

As noted, the invention can be applied advantageously to a skin-passmill. Here it is practical to install pickups in front of and after theroll stand which work together with the strip and which pick up thespeed of these strips, and a calculating device is provided to produce aquotient of the results of the pickups. This calculating devicespecifies its original datum as an actual value to a control devicewhich changes the roll separating force in the sense of a return of thequotient to a specified nominal or desired value. With this, theoperation of the roll bending cylinders is changed in proportion to theoperation of the hydraulic cylinders which effect the roll separatingforce.

According to the invention, unwanted strip tensions can be avoided whenpickups are installed ahead and following the roll gap of the stand,located over the width of the rolled stock, which pickup the thicknessesof the strip or its tensile stresses across the width of the stock. Inthis way, when differences in thickness or differences in the tensilestress are detected with the aid of a comparison device, values of whichare fed to the entrance of a control loop of the control device, thecontrol device influences the roll bending in the sense of reducing orabolishing the differences in thickness or the differences in tensilestress.

The invention can be applied to a two-high roll stand as well as othermulti-roll stands, such as four-high and cluster stands, and it isexplained by the following descriptions of examples of construction inconnection with drawings showing two-high and four-high mills. Thedrawings show the following:

FIG. 1 is a side view of a two-high skin-pass mill stand equipped withcounteracting bending bearings and roll bending cylinders indiagrammatic and partially sectioned representation;

FIG. 2 is one half of a section taken through the housing and the rollsof a four-high roll stand including pickups assigned to it, and acontrol device represented in block diagram form;

FIG. 3 is the skin-pass stand of FIG. 1 including rolls arranged infront of and behind the stand as well as speed and strip tensionmeasuring devices, diagrammatically shown in side view; and

FIG. 4 is a control device in block diagram form employed in conjunctionwith FIGS. 1 and 3 t operate a skin-pass mill.

FIG. 1 shows a side view of a mill stand 100 partially sectioned in aplane which lies in front of one of its two identical housings 101 thatmake up the mill stand. Since the housing and their components areidentical only one of the housings will be discussed. The housing 101has a window 102 in which bearing chocks 103 and 104 of working rolls105 and 106 are guided. The necks 107 and 108 of the rolls which arerotatably supported in the chocks 103 and 104 extend freely outward ofroll bodies 105 and 106, and they are equipped with chocks 109 and 110at their free ends as well as with roll bending bearings supported inthese chocks. The chocks 109 and 110 are constructed each with twosimilar C- shaped notches into which the end pieces 111 of piston rods112 engage. Levers 114 which are swingably around axes 113 connectedwith the housing 101 support hydraulic roll bending cylinders 115, eachof which is equipped with two opposite pistons associated with the rods112. The levers 114 are equipped with forks. Bolts 116 extend throughthe bores of each fork to which the piston rod of an hydraulic cylinder117 is attached. Each hydraulic operating cylinder is swingablyconnected to the housing 101. The end pieces 111 are heldin theiroperative position in the C-shaped notches formed in the chocks 109 andl with the aid of the hydraulic operating cylinders 115. The hydraulicroll bending cylinders 115 may be swung outwardly by the operating ofthe hydraulic cylinders 117, and the end pieces 111 can be pulled out ofthe notches of the chocks 109 and 110 to allow for changing of rolls 105and 106.

The bearing chock 104 is engaged by an hydraulic screwdown cylinder 118which is mounted on a pressure or load cell 119 supported by the housing101 and which in turn reproduces a signal proportional to the rollseparating force of the mill. The coarse adjustment of the roll gap isdone with the aid of a screwdown spindle 120 arranged at the top of thehousing 101, which is associated with a common constructed mechanicalscrewdown device 122 which engages a worm gear 121 secured to thescrewdown spindle.

A two-high stand has so far been described in which the necks of theworking rolls 105 and 106 are supported in bearing chocks in accordancewith common mill practice. The rolls are constructed with extended necksand equipped with roll bending bearings on their free ends in such amanner that expanding forces can be applied with the aid of roll bendingcylinders 115 which are capable of causing additional bending moments tothe working rolls while they are subject to bending caused by the rollseparating forces.

The effect, as well as the control of the screwdown cylinder 118 and ofthe roll bending cylinder 115, will be explained in detail by referringto FIG. 2 which shows a vertical section through the roll axes of afourhigh mill stand in connection with a control device assigned to itwhich is shown in block diagram form. For the sake of brevity, only theleft side of the mill stand from the mean vertical plane is shown in thedrawing. The right side while not shown is constructed identical to theleft side. The upper and lower yokes of the housing 1 are cut in thisparticular representation. The main bearings 3 and 4 of the backingrolls 5 and 6 are guided in chocks 7 and 8 in the housing window 2 ofthe housing 1. The backing rolls back up the working rolls 9 and 10, thenecks, bearings, and the chocks of which are not shown in this drawingfor simplicity sake. Backing rolls and working rolls enclose a roll gap11 in which rolled stock 12 is shown in this particular stand. While thechock 8 braces itself against the bottom of the housing window 2- whichis formed by the lower yoke of the housing, the chock 7 is screwed downwith the aid of an hydraulic screwdown cylinder 13. The screwdowncylinder 13 is associated with a pressure cell 14 which measures thesupporting forces which have to be produced by the screwdown device. Thescrewdown cylinder 13 is supported against the upper yoke of the housing1 with the aid of a removable block which can be replaced with blocks ofdifferent dimensions, and which allows for a coarse adjustment of thescrewdown mechanism. Wedge type or screwdown mechanisms using screwdownspindles can be applied instead of these blocks. The distance betweenthe chocks 7 and 8 caused by the blocks and screwdown cylinders 13 isconstantly measured by a motion or position pickup device 15 which isinductively active in the given example and which can be built as amagnetic amplifier.

In order to attain the dimensions of the main bearings 3 and 4 which arenecessary to transfer the high supporting forces, the necks 16 and 17 ofthe rolls 5 and 6 are constructed with a larger diameter in their rootarea 36 than in their other areas. For the reasons described later, thediameters of the bodies of the backing rolls 5 and 6 correspond to thediameters of the necks l6 and 17 of these rolls.

The free ends of the necks 16 and 17 of the backing rolls are equippedwith bending bearing assemblies 18 and 19 which are hydraulicallyexpandable with the aid of a back up roll bending cylinder 20. A motionor position pickup device 21 is arranged between the bearing 18 and 19and parallel to the back up roll bending cylinder 20, which can beconstructed inductively active, similar to the motion pickup device 15.

A pressure reservoir 22 is provided to operate the hydraulic screwdowndevices 13 of the stand as well as the back up roll bending cylinder 20.The pressure supply system for the pressure reservoir will follow commonmill practice, for which reason it has not been I shown in the drawing.It will be noted that the pressure reservoir 22 feeds servo valves 23and 24 inserted after it.

The working rolls 9 and 10 are screwed down with the aid of a controldevice 25 and a potentiometer 26 arranged ahead of the control deviceemployed to set the appropriate roll gap. The motion pickup 15 isconnected to the entrance 27 of the control device 25 and functions as apotentiometer The control device effects the servo valve 23 arrangedfollowing it and determines the admission of the compressive volume ofthe screwdown device 13 with the aid of the connection 28.

A control device 29 is equipped with two constant or pre-setpotentiometers 30 and 31, and it is designed to control the servo valves24, and with it, the admission of the backup roll bending cylinder 20. Avalue is specified with the aid of the constant or pre-set potentiometer30 which corresponds with a specified roll separating force and whichcauses a base admission to the backup roll bending cylinder 20 which inturn corresponds with this roll separating force. The roll separatingforce which has to be intercepted by the housing 1 is determined by thepressure cell 14 and then delivered to the control device 29 as anactual value. The control device causes an increase or decrease of theback up roll bending force brought about with the aid of the back uproll beding cylinder 20 in proportion to each increase or decreaserespectively of the roll separating force, at which the proportionalfactor is specified by the constant or pre-set potentiometer 31.

The proportional factor can be calculated based on the followingconsiderations: Starting from the assumption that the entire rollseparating force P is transferred pro rata to both housings; the rollseparating force P induced into the left half of the rolled stock 12 istransmitted by the housing 1 and represents a component of thesupporting force P A1 acting upon the pressure cell 14. With this, amoment is applied into the left halves of the working rolls 9 and 10,the sum of which results from the product of the one half of the rollseparating force P and the lever arm. The mean lever arm corresponds tothe distance a taken from the center of the main bearings 3 and 4, andthe center of the half width of the rolled stock; in other words, from apoint taken from between the adjacent first and second quarters of theentire width of the rolled stock. This moment is to be compensated forby a counter moment produced by the roll bending cylinders. The countermoment is determined by the restoring force P as well as by the leverarm b by which this force is applied at the distance between the centerof the roll bending bearings 18 and 19 and the center of the mainbearings 3 and 4.

Accordingly, an equilibrium is guaranteed as long as P a equals P b, andthe roll bending due to the rolling force will be totally compensatedfor. There is a tendency for a change to occur in the distance 0 of themain bearings 3 and 4 when the roll separating force changes, but thesechanges will be picked up by the motion pickup device and immediatelystabilized with the aid of the control device 25 and the quick actinghydraulic screwdown device 13, and the distance 0 will be maintainedpractically constant. With this, a control of the roll bending is alsoobtained since when the roll separating force changes, the distance c ismaintained constant and so is the distance d of the back up roll bendingbearings 18 and 19 until the control device 29 acts.

In order to strengthen this effect, the control device 29 is equippedwith a second control loop which keeps this distance specified by thepotentiometer 32 and/or by the connection 33 of the exit 34 of thecontrol device 25 constant: the distance d is picked up by the motionpickup 21 which is connected with the control device 29 as an inputsignal. For instance, an increase of the roll separating force whichwould cause the distance c to increase and the distance d to decreasewill be picked up by the control devices 25 and 29 which hold thesedistances constant. With this, not only the moment occurring in the rollbody is increased, but also the bending moment which is forced upon thenecks of rolls. In other words, when the roll separating forceincreases, the back up roll bending force increases at the same time,and the distances or the settings of the motion pickups l5 and 31 willbe maintained. Changes of the roll bending as well as changes of themean roll gap as a result of changes of the roll separating force willbe corrected automatically and without any time loss, and the shape ofthe strip and the thickness of the rolled stock as well as the skin passdegree, as it will be explained in detail in connection with FIGS. 3 and4, will be maintained at a constant level.

Changes of the desired thickness of rolled stock as well as adjusting tochanged widths of rolled stock can be obtained by changing thespecification of the actual value 26 of the pickup 15 as well as byadjusting the roll bending force P according to the changed rollseparating force P in relation to the lever arms a/b. This can be donefor one side of the stand as well as for both sides at the same time.

The roll bending can also be changed by introducing an additionalcorrection factor K in addition to the change with the aid of theproportional relation P P a/b. This too is possible for one side of thestand as well as for both sides at the same time, in order to make anadjustment to changes of rolling procedures such as variations of theroll body caused by roll etching, temperature variations, wear, changesof the entering strip sections, or changes of the lever arm a, as wellas of the resulting roll separating force P during rolling operation.

The principle of the control by applying the equality of moments and bymaintaining the distance 0 of the main bearings constant which can beconsidered as the point of rotaton of a scale balance system" has provento be of great advantage. It has proven to be of special advantage forfour-high roll stands to make the necks of the backup rolls-as far asthey are involved for backup bending-the same diameter as the rollbodies, and hence, with approximately the same moment of inertia, inorder to obtain the same characteristics for backup bending.Furthermore, it has proven to be of advantage when the diameters of theroll bodies and the necks of the rolls are maintained small. In thisway, very high expanding forces will be avoided in obtaining the desiredbending effect of the rolls as would otherwise be needed due to theirhigh moment of inertia, and, the fact that the necks of rolls must besubject to corresponding high bending stress by the expanding forces. Itis recommended to keep the difference between the diameters of the necksof the rolls and the roll bodies at no greater than 0.2.

Due to the compensation of the roll bending as described above, the rollbody can be kept considerably smaller in its diameter than what has beenthe case in the past. The large diameter of the roll body has beennecessary in the past to obtain a high inherent rigidity. In addition tothis, the strain of the roll bodies is greatly reduced by theapplication of the backup roll bending.

The system and the device of the present invention can be applied to atwo-high roll stand as well as fourhigh and cluster stands. As shown inthe drawing, the following relations of forces and moments result fromthe application of this system:

-Continued Since the proportioned roll separating force cannot bedetermined directly, and only the corresponding supporting force whichis the sum of the roll separating force and of the roll bending forcecan be determined with the aid of the pressure cell 14, the roll bendingforce can be calculated, adjusted and constantly controlled with the aidof the following equation:

In this case, as noted earlier, K represents the correction factor forthe adjusting of the roll bending to certain changes that take place inthe roll body and in the roll gap and preferably is 0.5 is than K 2.Changes of the roll separating force due to changes of the thickness ofthe entering rolled stock or changes of the deformation stability, andof the lubricating conditions, etc., will be automatically correctedaccordingly with the aid of a proportional change of the roll bending Pin addition to the pickup of the deviations of the load of the mainbearings P With this, a system for the bending of rolls is inventedwhich can be applied in many different ways. As long as the set ordesired distances c and d are maintained-- -and that applies especiallyfor rolls having roll bodies approximately equal in thickness with thenecks of the rolls--variations of the roll separating force areautomatically balanced without making a control device necessary. Thearrangements described which keep the distances constant assure thisresult. Furthermore, there is a simple procedure for determining thecounter moment, which has to be produced, beforehand. The applicationcan be further extended when the corresponding actual values can be madeto influence a controlled system and a simple operation in combinationwith the widest range of control can be guaranteed due to thecombination of the distance control and the control of the supportingforce.

Furthermore, it could prove to be practical to equip the exit side ofthe stand with monitors arranged over the width of the rolled stock. Thethickness distribution and/or the distribution of the tensile stress ofthe rolled stock can be determined with the aid of these monitors orwith the aid of measuring devices measuring the distribution of thetensile stress over the width of the strip, and further, corrections ofthe roll bending could be made manually or automatically with the aid ofanother control loop of the control device 29 which reached over theentrance 35 of the control device. A very low regulating speed isdesired for this control loop corresponding with the indirect controlwhich is brought about in this case.

Monitors, for instance, gauge measuring devices for the rolled stock,which may be constructed as X-ray devices, can also be used in order tomeasure the outgoing and/or the entering thickness of the rolled stockas actual value or as reference input to the control device 25 as afurther aid to maintain uniform thickness of the outgoing rolled stockwhich can be added to the control process and, with this, the tolerancesare further narrowed down. The monitors mentioned above can do this taskin which actual value can either be derived from only one of themonitors or an average can be taken from the measuring results ofseveral monitors.

The invention can be further altered. FIG. 3 shows in side view anarrangement as it can be used for surface dressing cold rolled strip.The strip 42 is drawn off from the strip coil 41 and conveyed over ameasuring roll 43 coupled with a tachometer 44 to the mill stand whichcorresponds with the stand shown in FIG. 1 as far as its structure isconcerned. After the strip has passed the roll gap of the stand, it isguided over another measuring roll 45 which is coupled with a tachometer46. A guide roller 47 finally conveys the strip to a reel 49 where it iscoiled. A measuring roll 48 is employed on the strip section between themeasuring roll 46 and the guide roller 47, which is equipped with ringssupported flexibly in an axial direction, the radial compressive loadapplication of which can be determined with the aid of measuringsystems, in order to determine the strip tension in various sections ofthe width. The construction and operation of the rolls 43, 45 and 48,can follow several well-known devices, al though the type disclosed inUS. Pat. No. 3,538,765 is preferred. The measuring rolls arranged aheadand following the roll gap in connection with the tachometer representspeed indicators with the aid of which it is possible to determine thequotient between the speed of the entering strip and the outgoing strip,and consequently, to determine the skin-pass rate of elongation.

A control arrangement to operate this skin-pass mill arrangement isshown in block diagram form in FIG. 4. The tachometers 44 and 46transfer signals of the tensions they measure to a comparison device 61.A potentiometer 62 is assigned to the tachometer 44 which is able toincrease the excitation of the tachometer 44 against the excitation ofthe tachometer 46. Its scale is gauged in percents of the excitation ofthe tachometer 46 so that by increasing the excitation of the tachometer44 for practically each existing skin-pass rate, uniform output voltagesof the tachometer may be set. The desired skin-pass rate will be setwith the aid of the potentiometer 62. Due to the increased excitation ofthe tachometer 44 which occurs with this, uniform output voltages ofboth tachometers are obtained. Meanwhile both the desired strip tensionand the outgoing speed which exceeds the entering speed by the desiredpercentage are maintained.

These output voltages can be compared by the following comparison device61 and the result will then be forwarded to a control device 63. If theskin-pass rate determined by measuring the speed and the formation ofquotients have proven to be too low, the servo valve 66 which is fed bya pressure reservoir 65 will be activated with the aid of the followingcontrol loop 64 including an intensifier, and the admission of thescrewdown cylinder 118 of the stand 100 shown in FIGS. 1 and 3 will beincreased to produce a higher screwdown force, which increases theskin-pass rate. Not until the roll separating force increases, due tothe increasing admission to the screwdown cylinder 118 to such an extentthat the desired skin-pass rate is obtained as determined by the voltagereceived by the comparison device 61 moving toward zero, will furtheradmission of the screwdown cylinder 118 be terminated. In order toobtain a more sensitive setting the regulating loop which activates thescrewdown cylinder 118 is constructed as control loop 64 which picks upthe voltage produced by the control device 63 as nominal value. Thiscontrol loop 64 receives in addition a signal in the form of the actualvalue of the separation force of the mill as determined by the pressurecell 119.

The roll bending cylinders 1 will admit fluid in proportion to theadmission to the screwdown cylinders 118. Principally, the admissioncontrol could also be taken off from the exit of the control device 63.For this purpose, a control loop 67 is provided which is directlycontrolled by the pressure signal of the pressure cell 119, in order toimmediately bring about an accurate and sensitive expanding force whichfollows every change of the roll separating force. The control loop 67influences a servo valve 69 which also is fed by the pressure reservoir65. The exits of this servo valve are connected with the hydraulic rollbending cylinders 115 shown in the FIGS. 1 and 3. The pressure in theseservo valves is picked up by a pressure pick-off 68 and transferred tothe control loop 67 as actual value, in

another comparison device 72. In case an asymmetry has been detected,this asymmetry will be transferred to the control loop 67 as anelectrical signal and, as another limiting quantity, it causes anadditional change of the admission of the roll bending cylinders untilthe expanding force reaches values that will cause the roll bending toguarantee a product with a constant tension distribution over the widthof the strip. In this case, it is not sufficient to keep the roll gapcompletely parallel and in uniform gauge over its length. For instance,it is not possible to obtain an outgoing material free of tension with auniform thickness over the length of the gap, when the entering strip isthicker in its center than on its edges. It is practical in this case,to change the roll bending expanding force slightly until a material isobtained which is free of tension. On the other hand, in a case ofsurface dressing a strip with slightly keystone or concave shapedsection, it could also be practical to subject the necks of the rolls ofboth housings of a stand with different expanding forces or, to letpotentiometers of the measuring roll act upon the control loops 64 of astand with the aid of comparison devices which are interpolated in adifferent arrangement so that not only different expanding forces can bebrought about but also different screwdown forces which are guided orcontrolled in such a manner that material with constant tensions overthe entire width of the strip leaves the roll gap.

It will be appreciated that the invention is not limited to the exampleof the construction illustrated. For instance, monitors can be used toadditionally pick up the width of the strip and the determination of thetensile stress of the strip could be useful for reduction rolling ofcold strips, for instance, in combination with a roll stand as shown inFIG. 2. It is also possible to provide for roll bending expanding forcesto be made proportional to the roll separating forces, when a thicknesscontrol and/or an adjustment of an advanced skin-pass rate is notemployed. In this case, it is practical to use the control loopsdetermining the expanding force in combination with measuring deviceswhich measure the tension distribution over the width of the outgoingstrip, and to control the expanding forces in such a manner thatmaterial will be obtained which is free of tension or which has aconstant tension over the entire width of the strip.

In accordance with the provisions of the patent statutes, I haveexplained the principle and operation of my invention and haveillustrated and described what I consider to represent the bestembodiment thereof.

I claim:

1. In a rolling mill having a housing and a pair of rolls between whichis formed a roll gap,

said pairs of rolls having bearing chock assemblies mounted on theirends received in said housing,

position indicating means arranged between at least one of saidcooperative opposed pair of bearing chock assemblies and capable ofproducing a signal representing the distance between said cooperativeopposed pair of bearing chock assemblies,

at least one of said rolls having free ends which are subject to rollbending forces of hydraulic roll bending piston cylinder assemblies, forthe purpose of compensating for at least some of the deflections of saidone roll caused by the separating force generated by said rolls duringrolling.

one of said rolls being adjusted by an hydraulic piston cylinderassembly screwdown arranged in said housing,

a pressure detecting means for producing a signal proportional to theseparating force, which signal is received by a control means,

means for connecting said control means with said roll bending pistoncylinder assemblies in a manner that the forces of said roll bending andscrewdown piston cylinder assemblies are maintained in a desiredproportional relationship relative to variations of the separatingforce, and

said control means receiving said distance signal and producing acontrol signal for effecting an operation of said screwdown to maintainsubstantially constant the distance between said cooperative opposedpair of bearing chock assemblies.

2. In a rolling mill having a housing and a pair of rolls between whichis formed a roll gap,

at least one of said rolls having free ends which are subject to rollbending forces of hydraulic roll bending piston cylinder assemblies, forthe purpose of compensating for at least some of the deflections of saidone roll caused by the separating force generated by said rolls duringrolling,

one of said rolls being adjusted by an hydraulic piston cylinderassembly screwdown arranged in said housing a pressure detecting meansfor producing a signal proportional to the separating force, whichsignal is received by a control means,

means for connecting said control means with said roll bending pistoncylinder assemblies in a manner that the forces of said roll bending andscrewdown piston cylinder assemblies are maintained in a desiredproportional relationship relative to variations of the separatingforce, and

said pair of rolls having bearing chock assemblies mounted on their endsreceived in said housing and wherein said proportional relationship isdetermined by a distance a drawn from a line dividing the adjacent firstquarter from the second quarter of the effective width of the roll stockand the center of the adjacent bearing chock assemblies on the one handand a distance b from a line coincident with the application of the rollbending force and the center of said adjacent bearing chock assembliesaccording to the equation:

where P represents the roll bending force, and P represents theseparating force.

3. In a rolling mill according to claim 2, wherein said proportionalfactor is modified by another factor K in which said K factor is greaterthan 0.5, but less than 2.

4. In a 4-high rolling mill having a housing including a pair of workrolls between which is formed a roll gap,

at least one of said backup rolls thereof having free ends which aresubject to roll bending forces of hydraulic roll bending piston cylinderassemblies, for

the purpose of compensating for at least some of the deflections of saidone roll caused by the separating force generated by said rolls duringrolling, and

wherein the diameters of the necks of said one backup roll is at least0.8 of the diameter of the roll body of said one backup roll,

one of said rolls being adjusted by an hydraulic piston cylinderassembly screwdown arranged in said housing,

a pressure detecting means for producing a signal proportional to theseparating force, which signal is received by a control means,

means for connecting said control means with said roll bending pistoncylinder assemblies in a manner that the forces of said roll bending andscrewdown piston cylinder assemblies are maintained in a desiredproportional relatonship relative to variations of the separating force.

5. In a 4-high rolling mill having a housing including a pair of workrolls between which is formed a roll gap, at least one of said backuprolls thereof having free ends which are subject to roll bending forcesof hydraulic rollbending piston cylinder assemblies, for the purpose ofcompensating for at least some of the deflections of said one rollcaused by the separating force generated by said rolls during rolling.said backup rolls having bearing chock assemblies received in saidhousing, and

the necks of the said one backup roll being constructed with diametersin the areas at which said bearing chock assemblies are mounted whichexceed the diameters of the necks and/or the diameters of the rollbodies of said one backup roll,

one of said rolls being adjusted by an hydraulic piston cylinderassembly screwdown arranged in said housing,

a pressure detecting means for producing a signal proportional to theseparating force, which signal is received by a control means,

means for connecting said control means with said roll bending pistoncylinder assemblies in a manner that the forces of said roll bending andscrewdown piston cylinder assemblies are maintained in a desiredproportional relationship relative to variations of the separatingforce.

6. In a 4-high rolling mill having a housing including a pair of backuprolls and a pair of work rolls, said work rolls forming a roll gap andwherein said backup rolls have bearing chock assemblies received in saidhousmg,

said backup roll having other bearing chock assemblies which are subjectto roll bending forces of hydraulic roll bending piston cylinderassemblies for the purpose of compensating at least some of thedeflections of said backup rolls caused by the separating forcesgenerated by said rolls during rolling,

position indicating means arranged between cooperative opposed bearingchock assemblies associated with said roll bending piston cylinderassemblies for measuring the distance between said opposed bearing chockassemblies,

said indicating means adapted to produce a signal representative of saiddistance,

one of said backup rolls being adjusted by an hydraulic piston cylinderassembly screwdown arranged in said housing,

a pressure detecting means for producing a signal proportional to theseparating force, which signal is received by a control means,

means for connecting said control means with said roll bending pistoncylinder assemblies in a manner that the forces of said roll bending andscrewdown piston cylinder assemblies are maintained in a desiredproportional relationship relative to variations of the separatingforce, and

said control means receiving said distance signal and including meansfor maintaining substantially constant said distance between saidcooperative opposed bearing chock assemblies associated with said rollbending piston cylinder assemblies.

7. In a rolling mill having a housing for receiving a pair of rollsbetween which is formed a roll gap,

at least one of said rolls having free ends which are subject to rollbending forces of hydraulic roll bending piston cylinder assemblies, forthe purpose of compensating for at least some of the deflections of saidone roll caused by the separating force generated by said rolls duringrolling,'

one of said rolls being adjusted by an hydraulic piston cylinderassembly screwdown arranged in said housing,

a pressure detecting means for producing a signal proportional to theseparating force, which signal is received by a control means,

means for connecting said control means with said roll bending pistoncylinder assemblies in a manner that the forces of said roll bending andscrewdown piston cylinder assemblies are maintained in a desiredproportional relationship relative to variations of the separatingforce,

roll stock engaging means arranged on the entry and delivery sides ofsaid roll gap for measuring the differences in thickness or in tensilestress transversely of the roll stock,

a thickness comparison means associated with said control means, and

said thickness comparison means being in the form of a control loopadapted to effect an adjustment of said roll bending in order to reduceor eliminate any detected difference in transverse thickness or tensilestress of said roll stock.

8. In a rolling mill according to claim 7 including a device forregionally measuring transversely the roll stock tension on the deliveryside of said mill,

said device including means for feeding a signal to a second controlloop,

said second control loop adapted to adjust said roll bending in a mannerthat differences in roll stock tension occurring over the width of theroll stock are maintained at a desired low level.

9. In a rolling mill having a housing for receiving a pair of rollsbetween which is formed a roll gap,

at least one of said rolls having free ends which are subject to rollbending forces of hydraulic roll bending piston cylinder assemblies, forthe purpose of compensating for at least some of the deflections of saidone roll caused by the separating force generated by said rolls duringrolling,

one of said rolls being adjusted by an hydraulic piston cylinderassembly screwdown arranged in said housing,

a pressure detecting means for producing a signal proportional to theseparating force, which signal is received by a control means,

means for connecting said control means with said roll bending pistoncylinder assemblies in a manner that the forces of said roll bending andscrewdown piston cylinder assemblies are maintained in a desiredproportional relationship relative to variations of the separatingforce,

speed determining means arranged on the entry and delivery side of saidmill and means associated therewith for determining the differencebetween the entry speed and the delivery speed of the said rolled stockand control speed means for producing a datum value of a desired speeddifference of the rolled stock and comparing it with said determineddifference in speed,

said control speed means including means for effecting operation of saidscrewdown piston cylinder assembly in order to return said determinedspeed difference to said desired value, and

said control speed means also including means for changing said rollbending piston cylinder assemblies in proportion to the change effectedin said screwdown piston cylinder assemblies.

UNITED arrrENT oFFIcE CERTIFICATE CORRECTION PAlENl' NO 3 8'77 270 DATEDApril 15, 1975 Hans-Friedrich Marten iiw'VENTOKiS:

It s certified t'r a r error appears in the above-Identified patent andthat said Letters Patent are hereby corrected as shown below- Column 1,line 48, "consturcting" should readconstructing; and

line 49, "fro" should readfor.,

Column 3, line 6, "ot" should readto-.

Column 5, line 8, "beding should readbending.

Column 7, lines '7 to 9, formula 6, that the two portions of the formulareading "p 1 and "iAP 1 H +1 1 a a should read PA1 1 l 0 19 +1 b 1 a ESigned and Scaled this twenty-second Day of July 1975 [SEAL] A nest:

RUTH C MASON Allesling Officer C. MARSHALL DANN Commissioner of Parentsand Trademarks

1. In a rolling mill having a housing and a pair of rolls between whichis formed a roll gap, said pairs of rolls having bearing chockassemblies mounted on their ends received in said housing, positionindicating means arranged between at least one of said cooperativeopposed pair of bearing chock assemblies and capable of producing asignal representing the distance between said cooperative opposed pairof bearing chock assemblies, at least one of said rolls having free endswhich are subject to roll bending forces of hydraulic roll bendingpiston cylinder assemblies, for the purpose of compensating for at leastsome of the deflections of said one roll caused by the separating forcegenerated by said rolls during rolling. one of said rolls being adjustedby an hydraulic piston cylinder assembly screwdown arranged in saidhousing, a pressure detecting means for producing a signal proportionalto the separating force, which signal is received by a control means,means for connecting said control means with said roll bending pistoncylinder assemblies in a manner that the forces of said roll bending andscrewdown piston cylinder assemblies are maintained in a desiredproportional relationship relative to variations of the separatingforce, and said control means receiving said distance signal andproducing a control signal for effecting an operation of said screwdownto maintain substantially constant the distance between said cooperativeopposed pair of bearing chock assemblies.
 2. In a rolling mill having ahousing and a pair of rolls between which is formed a roll gap, at leastone of said rolls having free ends which are subject to roll bendingforces of hydraulic roll bending piston cylinder assemblies, for thepurpose of compensating for at least some of the deflections of said oneroll caused by the separating force generated by said rolls duringrolling, one of said rolls being adjusted by an hydraulic pistoncylinder assembly screwdown arranged in said housing a pressuredetecting means for producing a signal proportional to the separatingforce, which signal is received by a control means, means for connectingsaid control means with said roll bending piston cylinder assemblies ina manner that the forces of said roll bending and screwdown pistoncylinder assemblies are maintained in a desired proportionalrelationship relative to variations of the separating force, and saidpair of rolls having bearing chock assemblies mounted on their endsreceived in said housing and wherein said proportional relationship isdetermined by a distance a drawn from a line dividing the adjacent firstquarter from the second quarter of the effective width of the roll stockand the center of the adjacent bearing chock assemblies on the one handand a distance b from a line coincident with the application of the rollbending force and the center of said adjacent bearing chock assembliesaccording to the equation: PR1 PA1 . 1/(b/a + 1) where PR1 representsthe roll bending force, and PA1 represents the separating force.
 3. In arolling mill according to claim 2 wherein said proportional factor ismodified by another factor K in which said K factor is greater than 0.5,but less than
 2. 4. In a 4-high rolling mill having a housing includinga pair of work rolls between which is formed a roll gap, at least one ofsaid backup rolls thereof having free ends which are subject to rollbending forces of hydraulic roll bending piston cylinder assemblies, forthe purpose of compensating for at least some of the deflections of saidone roll caused by the separating force generated by said rolls duringrolling, and wherein the diameters of the necks of said one backup rollis at least 0.8 of the diameter of the roll body of said one backuproll, one of said rolls being adjusted by an hydraulic piston cylinderassembly screwdown arranged in said housing, a pressure detecting meansfor producing a signal proportional to the separating force, whichsignal is received by a control means, means for connecting said controlmeans with said roll bending piston cylinder assemblies in a manner thatthe forces of said roll bending and screwdown piston cylinder assembliesare maintained in a desired proportional relatonship relative tovariations of the separating force.
 5. In a 4-high rolling mill having ahousing including a pair of work rolls between which is formed a rollgap, at least one of said backup rolls thereof having free ends whichare subject to roll bending forces of hydraulic roll bending pistoncylinder assemblies, for the purpose of compensating for at least someof the deflections of said one roll caused by the separating forcegenerated by said rolls during rolling. said backup rolls having bearingchock assemblies received in said housing, and the necks of the said onebackup roll being constructed with diameters in the areas at which saidbearing chock assemblies are mounted which exceed the diameters of thenecks and/or the diameters of the roll bodies of said one backup roll,one of said rolls being adjusted by an hydraulic piston cylinderassembly screwdown arranged in said housing, a pressure detecting meansfor producing a signal proportional to the separating force, whichsignal is received by a control means, means for connecting said controlmeans with said roll bending piston cylinder assemblies in a manner thatthe forces of said roll bending and screwdown piston cylinder assembliesare maintained in a desired proportional relationship relative tovariations of the separating force.
 6. In a 4-high rolling mill having ahousing including a pair of backup rolls and a pair of work rolls, saidwork rolls forming a roll gap and wherein said backup rolls have bearingchocK assemblies received in said housing, said backup roll having otherbearing chock assemblies which are subject to roll bending forces ofhydraulic roll bending piston cylinder assemblies for the purpose ofcompensating at least some of the deflections of said backup rollscaused by the separating forces generated by said rolls during rolling,position indicating means arranged between cooperative opposed bearingchock assemblies associated with said roll bending piston cylinderassemblies for measuring the distance between said opposed bearing chockassemblies, said indicating means adapted to produce a signalrepresentative of said distance, one of said backup rolls being adjustedby an hydraulic piston cylinder assembly screwdown arranged in saidhousing, a pressure detecting means for producing a signal proportionalto the separating force, which signal is received by a control means,means for connecting said control means with said roll bending pistoncylinder assemblies in a manner that the forces of said roll bending andscrewdown piston cylinder assemblies are maintained in a desiredproportional relationship relative to variations of the separatingforce, and said control means receiving said distance signal andincluding means for maintaining substantially constant said distancebetween said cooperative opposed bearing chock assemblies associatedwith said roll bending piston cylinder assemblies.
 7. In a rolling millhaving a housing for receiving a pair of rolls between which is formed aroll gap, at least one of said rolls having free ends which are subjectto roll bending forces of hydraulic roll bending piston cylinderassemblies, for the purpose of compensating for at least some of thedeflections of said one roll caused by the separating force generated bysaid rolls during rolling, one of said rolls being adjusted by anhydraulic piston cylinder assembly screwdown arranged in said housing, apressure detecting means for producing a signal proportional to theseparating force, which signal is received by a control means, means forconnecting said control means with said roll bending piston cylinderassemblies in a manner that the forces of said roll bending andscrewdown piston cylinder assemblies are maintained in a desiredproportional relationship relative to variations of the separatingforce, roll stock engaging means arranged on the entry and deliverysides of said roll gap for measuring the differences in thickness or intensile stress transversely of the roll stock, a thickness comparisonmeans associated with said control means, and said thickness comparisonmeans being in the form of a control loop adapted to effect anadjustment of said roll bending in order to reduce or eliminate anydetected difference in transverse thickness or tensile stress of saidroll stock.
 8. In a rolling mill according to claim 7 including a devicefor regionally measuring transversely the roll stock tension on thedelivery side of said mill, said device including means for feeding asignal to a second control loop, said second control loop adapted toadjust said roll bending in a manner that differences in roll stocktension occurring over the width of the roll stock are maintained at adesired low level.
 9. In a rolling mill having a housing for receiving apair of rolls between which is formed a roll gap, at least one of saidrolls having free ends which are subject to roll bending forces ofhydraulic roll bending piston cylinder assemblies, for the purpose ofcompensating for at least some of the deflections of said one rollcaused by the separating force generated by said rolls during rolling,one of said rolls being adjusted by an hydraulic piston cylinderassembly screwdown arranged in said housing, a pressure detecting meansfor producing a signal proportional to the separating force, whichsignal is received by a control means, means for connecting said controlMeans with said roll bending piston cylinder assemblies in a manner thatthe forces of said roll bending and screwdown piston cylinder assembliesare maintained in a desired proportional relationship relative tovariations of the separating force, speed determining means arranged onthe entry and delivery side of said mill and means associated therewithfor determining the difference between the entry speed and the deliveryspeed of the said rolled stock and control speed means for producing adatum value of a desired speed difference of the rolled stock andcomparing it with said determined difference in speed, said controlspeed means including means for effecting operation of said screwdownpiston cylinder assembly in order to return said determined speeddifference to said desired value, and said control speed means alsoincluding means for changing said roll bending piston cylinderassemblies in proportion to the change effected in said screwdown pistoncylinder assemblies.